The fetus, as a patient, is relatively inaccessible to the physician and, thus, presents genuine problems to monitor its well-being. The majority of intrapartum fetal deaths can be avoided by continuous fetal monitoring. Endocrine assessment of the complex maternal-fetal-placental unit is one approach to early recognition of fetal distress. Steroid hormones offer significant advantage in this regard, since biosynthesis of estrogens, particularly estriol, E3 involves fetal, organs such as liver and adrenal as well as placenta and maternal liver. Estetrol E4 is another steroid produced by fetal liver and has no circadian rhythm. Serum unconjugated estriol (E3) assays are widely utilized during the third trimester of complicated pregnancy. However, the clinical usefulness of such assays is debatable. Daily serum E3 measurements are required for predictable results. In routine clinical practice, maternal blood samples are difficult to collect more than once or twice a week. Weekly or biweekly results are disappointing, particularly in problem pregnancies. Saliva offers an alternative source for daily assessment of E3. Kundu et al. have already shown its usefulness by radioimmunoassay (RIA) of E3 in saliva. Although E3 provided the basis for assessment of pregnancy status, determination of E4 level (a product of fetal liver) will be a particularly sensitive and reliable indicator of fetal well-being. It is also assayed by RIA in a few laboratories. However, RIA is a sophisticated procedure requiring special reagents, radioactive ligands and spectrometer for radioactivity determination. This assay is expensive and labor-intensive. The present proposal aims to 1) develop specific monoclonal and polyclonal antibodies to E3 and E4 and 2) prepare specific antibody reagents for non-isotopic immunoassay kits for use at home or in hospitals. These specific and highly sensitive assays will be simple and reliable. They will provide obstetricians with tools to monitor the functional status of fetal liver and adrenal on a routine basis.